The other day I gave a talk to a parents’ group at a boys’ school. It was a big group. I asked them if they’d ever known a boy who hadn’t made a pretend gun with his fingers and gone bang-bang. Not a single hand went up.

No surprise there. Boys have been fighting with pretend weapons since the dawn of time. Mock battles and mock violence are a normal part of boyhood. But in the age of zero tolerance and Sandy Hook, society is in a panic. Some parents won’t allow water guns in the house. Even Nerf Blasters aren’t okay. “[Parents] think it’s innocuous because it’s a cartoon,” one critic of toy guns told The New York Times. “But they’re buying something that is reinforcing shooting.”

Last month, a five-year-old Massachusetts boy was threatened with a two-week suspension from his after-school program for making a gun from Lego bricks. “Pointing a gun and making shooting sounds can be uncomfortable to somebody. And it’s not respectful,” explained the earnest school superintendent in an interview with ABC. In Maryland, a six-year-old was suspended for one day for – yes – pointing his finger like a gun. His parents hired a lawyer to have the suspension removed from his permanent record.

The punishment of boys for being boys proceeds apace. But what happens to them on the playground is the least of it. What happens in the classroom is worse.

New evidence suggests that boys are penalized from the day they first set foot in school. A new study (whose findings were first reported by Christina Hoff Sommers, writing in The New York Times) finds that boys get lower grades than girls across the board – not because their schoolwork is inferior, but because they don’t behave like girls.

The study, which was published in The Journal of Human Resources, compared the standardized test scores of thousands of kids in kindergarten through Grade 5 with the grades their teachers gave them. Overall, girls outperformed boys on reading tests, boys outperformed girls on science tests, and boys and girls scored about the same in math. But no matter what the subject, the boys’ grades did not reflect their test scores.

“Boys who perform equally as well as girls on reading, math and science tests are graded less favourably by their teachers,” the authors write. Why? Because of differences in “non-cognitive development” – that is, behaviour. In general, girls are much better at sitting still, paying attention and co-operation – all the traits that teachers value. Boys lose points because of that. And the bias against boys, the study found, begins in kindergarten.

Why does this matter? Because how you do in school increasingly dictates how you will do in the world. And teachers’ grades strongly influence grade-level placement, high-school graduation and university admission prospects.

Some people argue that it’s only fair to mark boys down for deportment. To me, that’s gender bias. It’s like saying that women aren’t as promotable as men because they don’t behave the way men do in the workplace.

It’s no surprise that schools subtly discriminate against boys. After all, they are increasingly run by women – women who, as girls, were extremely good at sitting still, paying attention and co-operating. The schools have become more and more hostile to boys’ inclinations and interests. They have abolished competition in favour of co-operation – even though boys thrive on competition. They’ve outlawed rough-and-tumble play (too dangerous) and even cancelled recess altogether. In high school, they bore boys to death instead of teaching them how to make and build stuff.

One of the most successful schools today (also cited by Ms. Sommers) is New York City’s Aviation High School, whose students are mostly minority boys from low-income families. Students spend half the day in standard classes and the other half studying technical subjects such as aviation hydraulics and aircraft engines. They wear coveralls and get to practise on real planes. The school day is extremely long, and graduation rates are exceptionally high.

We have a good community-college system in Canada. But that comes too late for a lot of boys. We need a massive reinvention of vocational schools, turning them from dumping grounds into places where boys can learn and thrive. Boys will be boys. Work with it.